Find the positions of the minimums of the values of an array at labels.

Parameters :

input : array_like

Array_like of values.

labels : array_like, optional

An array of integers marking different regions over which the
position of the minimum value of input is to be computed.
labels must have the same shape as input. If labels is not
specified, the location of the first minimum over the whole
array is returned.

The labels argument only works when index is specified.

index : array_like, optional

A list of region labels that are taken into account for finding the
location of the minima. If index is None, the first minimum
over all elements where labels is non-zero is returned.

The index argument only works when labels is specified.

Returns :

output : list of tuples of floats

Tuple of floats or list of tuples of floats that specify the location
of minima of input over the regions determined by labels and
whose index is in index.

If index or labels are not specified, a tuple of floats is
returned specifying the location of the first minimal value of input.